Which synthetic organic pesticide is considered the most toxic?

Organophosphates are classified as some of the most toxic synthetic organic pesticides due to their mechanism of action, which interferes with the normal functioning of the nervous system. They inhibit the enzyme acetylcholinesterase, leading to an accumulation of the neurotransmitter acetylcholine. This disruption causes overstimulation of nerve cells, which can result in severe physiological effects, including convulsions, respiratory failure, and potentially death in high exposures.

While the other classes, such as carbamates and organochlorines, also have their own significant toxicities and health concerns, organophosphates are particularly notorious for their acute toxicity and ease of absorption through skin and inhalation. Pyrethroids, on the other hand, tend to have a lower acute toxicity for humans and are generally considered safer, especially in household use.

Thus, the organophosphates' ability to cause swift and severe toxic effects makes them the most toxic among the listed synthetic organic pesticides.